An exhaust treatment apparatus is mounted on such a work vehicle as a hydraulic excavator, a bulldozer, and a wheel loader. As the exhaust treatment apparatus, for example, a diesel particulate filter apparatus (DPF), a diesel oxidation catalyst apparatus (DOC), a selective catalytic reduction apparatus (SCR), and the like are available.
An exhaust treatment apparatus reduces a nitrogen oxide (NOx) contained in a gas exhausted from an engine (an exhaust gas), to a harmless gas through NOx reduction reaction. A work vehicle includes a reducing agent tank for storing a reducing agent for NOx reduction reaction, and the reducing agent stored in the reducing agent tank is injected into the exhaust gas.
In this regard, when a reducing agent stored in a reducing agent tank runs out during working of a work vehicle, an exhaust gas may be emitted into the air without NOx reduction reaction.
Therefore, Japanese Patent Laying-Open No. 2007-321671 and Japanese Patent Laying-Open No. 2007-321672 propose a scheme for urging an operator to replenish a reducing agent tank with a reducing agent by detecting an amount of remaining reducing agent stored in the reducing agent tank and controlling an engine to low output when the detected remaining amount is equal to or lower than a prescribed amount.